Covering material



1 Ju1y1s,1944 A MaoNuTT 2,353,680

covERING MATERIAL Filed Feb. 18,l 1941 l INVENTOR ATTORNEY' PatentedJuly 18, 1944 COVERING MATERIAL.

Arthur D. MacNutt, Kenmore, N. Y., assgnor to. Certain-Teed ProductsCorporation, New York, N. Y., a corporation'of Maryland ApplicationFebruary 18, 1941, Serial No. 379,428

5 Claims.

This invention relates to covering materials which are intended to beimpervious and weather resisting. More especially the invention relatesto impregnated felted sheets carrying thereon a protective weather andwaterresisting coating. More particularly, the invention relates toasphaltl roong and shingle elements.

Protective coatings as above broadly described are typified by so-calledasphalt rooiing in which in common .practice a lbase sheet of ieltedfibre is impregnated with bituminous saturant, usually asphalt, to bondthe fibres together and to provide in part the weather-resistingcharacteristic of the covering. Ordinarily in coverings which are to beexlposed to the Weather, such as roll roofing and shingles, upon sucha"saturated, that is an impregnated, felt sheet as a. Ibase a coating ofhigh melting point asphalt is applied of such thickness and of suchcomposition and consistency as to form the impervious overlying layeradhering to the saturated base. In many cases for decoration and forbetter protective capacity a granular surfacing material, ordinarily ofmineral origin, is applied to the coating to adhere thereto. .Thissurfacing affords resistance to mechanical abrasion and should be opaqueto intercept the light and prevent actinic action of the suns rays uponthe bituminous materials.

It is desirable in such covering materials to have v a. thoroughlyimpregnated base felt and to have a uniformly spread coating and onecompletely covering and sealing the base sheet, that is, withoutopenings therethrough.

In the ordinary methods of manufacture now in use while the process isbeing carried on a. fairly high degree of impregnation may be obtainedand a substantially complete covering of the faces of the base by thecoating may be secured. Nevertheless, in commercial practice it has vsofar not been possible to produce a covering or roofing sheet of iibrousmaterial so thoroughly impregnated that air andmoisture, and especiallymoisture, are completely excluded from and are prevented from beingabsorbed by the finished sheet. Because of the condition thattheimpregnation and coating operations ordinarily take place with thematerials ata.- high temperature, i. e., of the degree of 300 to 450 F.,and for other reasons, air and moisture commonly are contained withinthe finished saturated and coated sheet, being drawn thereinto uponcontraction of the impregnating and coatinggiaterials upon cooling orbeing absorbed after the covering is shipped or 'put into service.

Because the usual process of applying the coating to the base involvesrunning the sheet through a, bath of the high melting point asphalt,

whereby the coating becomes applied to bothsides of the sheet, air andmoisture may become entrapped within the saturatedfelted structure ofthe sheet. I This may be the case even though the coating on the backside may be reduced' by scraping to a relatively thin layer. The highmelting pointlcoating asphalt tends to ll the surface ,pores orinterstices of the impregnated felt on its outer face and upon settingat ordinary air temperatures to prevent easy passage of the entrappedair and moisture outwardly from the saturated base when expansion of theair and vapor occurs as the roofing becomes heated, forA example, underthe heat of the sun.

One of the difficulties resulting from these conditions is thatexpansion of the air and moisture Within the impregnated feltedstructure may bulge the coating upon the base sheet. Whenroofing. Thesheet then ceases to be impervious to water and becomes unsightly, theappearance being marred by the resulting uneven surface and the exposureoiv asphalt Where the granules are pushed oi. The more or less capillary'passages by which at leisure air and particularly moisture have enteredthe body of the impregnated felted structure do not afford suicient areaof discharge when the covering becomes rapidly heated with concomitantexpansion of the entrapped air and moisture. Rupture of the enlargedbubbles or pockets of air or vapor isl the result. 4

It is an object of the invention to overcome these diiiiculties and tominimize the blistering and effects thereof. i

It isa further object of the invention to produce a covering in whichprovision is made for release of the air or vapors as they becomeheated.

It is another object of the invention to provide a. process of producingsuch rooiing or covering.

' While in the past it has been thought that the application of coatingmaterial to the underside or back face of the rooiing sheet or shingleserved to improve the resisting qualities of the roofing and itsdurability, this undercoating has been of little service for thispurpose. The greatest resistance to water and the action of the elementsmust be on the outer face of the roong.

'I'he coating which is applied to the under face becomes detrimentalfrom the viewpoint of the` tendency of the-roofing to blister for thereasons I which have been given above.

According to theinvention it is proposed to form perforations in thebase sheet extending from the back or under face thereof into the tionss. llo and u.

tions and in view of their being open at the.

under face of the rooilng, when the pocket of air or vapor tends to formand expand under the heat of the sun it is possible for this air ormoisture under the pressure caused by the heating to und relief throughone or more of the perforations and to be discharged at the back face ofthe sheet. While in many cases a perforation may actually extend to sucha pocket, in other cases the expansion may take place a short distancethrough thevfelted structureitself until it reaches a perforation. Asuilicient number of -perforations close enough together are formed inthe sheet according to the invention to limit the size to which a pocketmay increase before finding relief through the perforation. Theperforations also will be so spaced that the pockets which may tend toform just beneath the coating on the outer or weather face of therooiing will not increase to such an extent before reaching aperforation that a blister of any substantial size will be formed. Thusthe 'pushing olf of the coating and the resulting deterioration andmarring of the appearance will be prevented. l

The action which has been referred to is assisted by the characteristicof the outer or weather resisting coating of the rooilng which causes itto strongly adhere to the saturated base sheet and because of its havinga substantial thickness. The consistency or density of the coating inits set condition at ordinary temperatures, moreover, causes it toailord a substantial barrier against which the expanding gases and vapormay act providing they can und outlet toward the opposite face of theroofing. As the coating is of plastic nature, however, and particularlyis thermoplastic under the heat of the sun, this resistance affording abarrier becomes greatly reduced when heated so that the blistering mayoccur unless the relief which the invention provides is available.

The figure in the drawing shows a crosssection of a roofing sheetembodying the invention.

In the iigure the base sheet I isa felt as ordinarily used in themanufacture of asphalt roofing, which is impregnated with an asphalt"saturant of .so-called low melting point. As in ordinary rooiingmanufacture upon the back side, that is, the underside of the rooilngwhich would be next to the roof deck, a relatively thin back coating 3is applied as in the ordinary roong. Upon the opposite face of theimpregnated base I the usual weather resisting coating 5 is applied soas to adhere to the impregnated felt base. In the partciular exampleillustrated in the drawing, granules l are applied to the coating 5 andembedded part way therein to afford a mechanical abrasion resistingsurfacing and one which intercepts the actinic rays of the sun. Y

Throughout the extent of the roofing sheet and in spaced relation areprovided perforal These perforations extend from the back face into theimpregnated vfelted structure of the base. Some of these perforations,such as 9, extend only a short distance into the felted structure.Others, such as I0, extend to a greater distance and still others, suchas II, extending substantially to the face of the base upon which theouter or weather coating adheres. The spacing of the perforations 9, Il)and II may be of the degree of between 312" and ik" in order that thesize of any blister which may start to develop between two perforationsmay be limited. VI n other words, as the pocket or blister tends toincrease by expansion of the gas or vapor contained therein in generalits increase in any lateral direction will not need to be greater thanabout half of the distance between -two perforations in order to iindrelief. The development of large Vsize pockets which heretofore havecaused blistering is prevented.

It will be clear that the perforations are open at the back face of thesheet. This is accomplished by making the perforations in the niihedsheet, that is, the sheet to which the coating has been applied, sincein ordinary roofing practice it is more convenient to apply iirst thecoating to both faces of the impregnated sheet. By passing the sheetthrough a coating bath a certain amount of coating may remain upon theback face even though its thickness is substantally reduced by passingthe dipped and coated sheet over a. scraper or other device for removaland limitation of the thickness of this back coating. After passing fromthe coating bath the sheet may be carried over a roll having thereonpins or spines of varying lengths and if desired of varying diameters sothat the spines will enter the coated base from the back or `under facethereof to form the perforations in the manner and arrangement shown andabove described. The lengths of the pins or spines, however, should notbe such as to puncture the coating on the outer face of the sheet. 'I'hesheet may be thus passed over the 'perforating roll after the coatinghas set to the desired degree so that the back coating will not tend toclose over the open ends of the perforations which are at the back face.To secure the action desired according to the invention these ends ofthe perforations should be left open so that ready escape of theexpanded gas and vapor may take place.A

To accomplish the results which have been described in a practicalmanner and with apparatus and devices adaptable in the ordinary roofingmachines, the roll referred to above should be of substantial diameterin order that as the roofing sheet moves tangentially into contact withthe roll the motion of the pins on the circumference of the roll will bein a path which is not at a great angle to the sheet. Especially forthose pins which are of such length as to pass through the impregnatedbase substantially to the underside of the barrier coating, such alimited angularity of approach is desirable in order that these pinsshall not tear the base or too greatly enlarge the perforations whichthey are intended to make during their approach to and recess from theroofing sheet.

In some cases, in view of variations in the thicknesses of the basesheets which pass thereover it may occur that the outer extremities ofthe longer pins will enter the barrier coating to some extent. A slightentrance or indentation of the barrier coating from the underside willnot be objectionable. As indicated above, howeuer,

the length of the pin or spine should be limited so as not to so farenter the coating that the" coating will be punctured or will becomepunctured by expansion of a bubble or pocket of gas or vapor. It isimportant that the outer coating shall not lose its function as'thebarrier acting to force the gas and vapor toward the back face of thesheet. For the purposes of ordinary asphalt roofing sheets, therefore,the length of the pins or spines may varyfrom .020 to .100.

The diameter of these pins or spines is determined in considerationoftheir necessary strength and resistance to bending and to wear as thesheet is passed thereover and while also considering the function of thepins or spines of producing a perforation of sufficient crosssectionlarea for leako of the gas or vapor to provide the desired relief. Thediameter or. crosssection of the pin or spine should` be so limited,however, that it will readily enter the impregnated felt structurewithout so deforming the general lay of the impregnated base that itsstructure and the appearance of the iinished roofing sheet willbechanged. Such displacement of the material of the impregnated basemust be effected, nevertheless, as'to form a perforation with thenecessary cross-section to insure that the cumulative area of theperforations will provide relief throughout the sheet for any gas orvapor which is entrapped or contained therein. For the purposes ofordinary asphalt roofing manufacture the diameter of the pins c-r spinesmay be from .010" to .100".

In consideration of the limitations of the dimensions of the pins andspinesto produce perforations suitable for the invention, for practicalasphalt roong manufacture the spacing of the perforations, that is, ofthe pins and spines upon the roll, is within the range of 1/8 to V4"from center to center of the pins. 'I'hese perforations,.however, may bemade in the sheet in staggered arrangement or in alignment lengthi wiseand crosswise of the sheet. Y

The invention has been described in its particular embodiment inconnection with a roofing sheet impregnated with asphalt and coated withcoating asphalt. It is, however, not limited to such materials but isapplicable to coverings which are formed with a base, particularly animpregnated base, in which a certain amount of air, gas or vapor iscontained which is subject to expansion upon being heated. It is aparticular feature of the invention thata coating adheres to the face ofthe base opposite to that from which the perforations extend, .whichcoating is of such character, of such thickness and Yconsistency, as toafford a barrier substantially impervious to the passage therethrough ofgaseous and vaporous material to force these gaseous and vaporousmaterials as they expand to pass out at the back face of the sheet.

The product of the invention may be produced by other methods than thatwhich is carried out with the spined roll above described. For example,the sheet of roong or a roo'ng element may be placed in a platen type ofpress having the spines upstanding from one of the platen faces. As thesheet or element is pressed between the platens the spines will enterthe face of the sheet or element to form the perforations.

Also, Within the scope of the invention, the impregnated base sheet mayhave perforations formed therein before the barrier coating is appliedto the face of the sheet. Any of the perforations which may extend tosaid face of the as 1s desirable. Care should be taken, however, thatany coating applied to the back or underface of the sheet does not closethe ends of the perforations which are at this back face.

Having thus described my invention I now claim:

1. A roong sheet comprising a. base of felted structure having upon avface thereof a coating of plastic adhesive material in set conditionadhering to said face, said coating in said set condition beingsubstantially impervious to passage therethrough of gaseous or vaporousmaterial,l said Abase being perforated from the face thereof opposite tothat to which said coating adheres, said perforations extending withinthe structure of said felted base to provide leakoif passages for gasesand vapors contained Within theA felted structure.

2. `A roofing sheet comprising a base of felted structure impregnatedwith an impregnating material in plastic condition, said impregnatedbase having adhering to a face thereof a coating of plastic adhesivematerial in set condition, said coating in said set condition beingsubstantially impervious to passage therethrough of gaseous or vaporousmaterial, said `base being perforated from the face thereof opposite tothat to which said coating adheres, said perforations being open at saidopposite face and extending within the structure of said impregnatedfelted base to provide leakoff passages for gases and vapors containedWithin said impregnated base.

-3.. A roong sheet comprising a base of yfelted structre impregnatedwith a thermoplastic ma.

a face thereof a coating of thermoplastic material, said coating in setcondition being substantially impervious to passage therethrough ofgaseous or vaporousmaterial, said impregnated base being perforated fromthe face thereof opposite to that to which the thermoplastic coatingadheres, said perforations extending within said impregnated base andproviding leakoif passages for gases and vapors contained within theimpregnated felted structure.

4. A roofing sheet comprising a base of felted structure impregnatedwith an asphalt saturant, said impregnated base having adhering to aface thereof a coatingv of asphalt capable of setting at air tempeaturesto form a barrier to passage therethrough of gaseous or vaporousmaterial, said .impregnated base being perforated from the face thereofoppositeto that to which the asphalt coating adheres, said perforationsextending Within said impregnated base and providing passages fordischarge at said oppOsite face of gases and vapors contained withintheimpregnated base. v

5. A roofing sheet comprising a. base of felted structure impregnatedwith an asphalt saturant, said imprengated base having adhering to aface thereof a coating of asphalt capable of setting at air temperaturesto form a. barrier to passage therethrough ofk gaseous or vaporousmaterial, said impregnated base being perforated from the face thereofopposite to that to which the asphalt coating adheres, said perforationsextending within said impregnated base and providing passages fordischarge at said opposite face of gases and vapors contained within the'impreg-f

